Angiopoietins (Ang) 1-4 have all been shown to bind to and activate Tie2 receptor tyrosine kinase activity to differing extents. All the Angs are characterized structurally by an N-terminal super clustering domain (SCD) followed by a coiled-coil domain (CCD) and a C-terminal fibrinogen-like domain (FLD) (Ward and Dumont 2002; Tsigkos et al. 2003). Functional studies have highlighted a role for the SCD and CCD's in forming high order homotypic multimers of Ang (Procopio et al. 1999). The specific nature of these multimers is variable and is unique to each Ang family member. Binding specificity of the Angs for the Tie2 receptor has been ascribed to the FLD (Tisgkos et al. 2003; Procopio et al. 1999). Taken together, it is the unique structural attributes of each Ang family member that promotes binding and differential clustering of Tie2. The pleiotropic physiological effects of Angs 1-4 are thought to at least in part be mediated by appropriate and specific clustering of the receptor. For instance mice engineered to overexpress the CCD of Ang 1, capable of multimerizing with endogenous Ang1 produced in the same cell, caused improper patterning of the coronary vessels (Ward et al. 2004). Furthermore, chimeric forms of Ang 1 engineered to contain the C-terminal FLD and one of several different CCD's differed in their ability to activate the Tie2 receptor (Cho et al. 2004a; Cho et al. 2004b).
Based on this information, the present inventors previously designed a peptide mimetic, called Vasculotide, that binds to Tie2 and when configured as a tetramer results in the clustering of the receptor and its activation.
Activating Tie2 through the tetramerization of high affinity Tie2 binding peptides using the biotin/avidin model (Van Slyke et al. 2009) has established the use of the peptide as an agonist to the Tie2 receptor to promote angiogenesis for applications in diabetic wound healing and other cardiovascular indications.
Patients with allergic diseases respond to an allergen with a systemic response that initiates the production of specific inflammatory cells, eosinophils and basophils and their progenitors, from the bone marrow (Denburg and Keith 2008; Hogan et al. 2008; Rothenberg and Hogan 2006). Upon release of these cells from the bone marrow they usually target the respiratory mucosa and other tissues and once activated eosinophils and basophils are one of the key immunomodulatory cells that sustain the allergic response (Rothenberg and Hogan 2006; Barrett and Austen 2009; Gauvreau et al. 2009; Schroeder 2009). These cells are known to secrete TGF-β, which is known to be an extremely potent pro-fibrogenic factor (Jacobsen et al. 2007; Hogan 2007; Raap and Wardlaw 2008).